Fuel compositions

ABSTRACT

Unleaded blend compositions, as well as formulated gasolines containing them have a Motor Octane Number (MON) of at least 80 comprising at least 10% of component (a), which is at least one branched chain alkane of 8-12 carbons with at least 4 methyl or ethyl branches, and as component (b) at least 20% of at least one, liquid hydrocarbon or mixture thereof of bp60-160° C., especially of MON value at least 70 and RON at least 90 or as component (b) at least 20% of one or more refinery streams. The component (a) gives rise to reduced emissions to the composition or gasoline on combustion.

[0001] This invention relates to a fuel composition, in particular agasoline composition for transportation uses e.g. use in motor vehiclesor aircraft.

[0002] For many years manufacturers of spark ignition combustion engineshave been striving for higher efficiency to make optimum use ofhydrocarbon based fuels. But such engines require gasolines of higheroctane number, which has been achieved in particular by addition oforgano lead additives, and latterly with the advent of unleadedgasolines, by addition of MTBE. But combustion of any gasoline givesrise to emissions in the exhaust gases, e.g. of carbon dioxide, carbonmonoxide, nitrogen oxides (NOx) and toxic hydrocarbons and suchemissions are undesirable.

[0003] Unleaded gasolines have been discovered having high Octane Numberbut producing low emissions on combustion.

[0004] The present invention provides an unleaded blend compositionhaving a Motor Octane Number (MON) of at least 81 or 85 and ResearchOctane Number (RON) of at least 91 or 94 which comprises component (a) atotal of at least 10% or 15% by volume of the blend composition of atleast one branched chain hydrocarbon, which is an alkane of 8-12 carbonatoms with at least 4 methyl or ethyl branches (hereinafter called acompound (A) there being a minimum of at least 1, 2, 5 or 10% by volume(of the blend composition), of at least one individual compound (A) andcomponent (b) at least one liquid hydrocarbon or mixture thereof ofbp60-160° C. having a MON value of at least 60 preferably at least 70and RON value of at least 70 preferably at least 80 and especially atleast 90, the total amount of component (b) being at least 20%, with thepreferred proviso that the blend composition contains less than 5% of223 trimethyl pentane, and especially less than 1 or 0.5%, andespecially less than 0.5%, in total of 223 trimethyl butane and 223trimethyl pentane

[0005] In another aspect the present invention provides an unleadedblend composition of MON value of at least 81 or 85 and RON value of atleast 91 or 94 which comprises component (a) as defined above and ascomponent (b) at least 20% in total of one or more refinery streams,such that the blend composition contains in total at least 70% ofsaturated hydrocarbons.

[0006] Unless otherwise stated all percentages in this specification areby volume, and disclosures of a number of ranges of amounts in thecomposition or gasoline for 2 or more ingredients includes disclosuresof all sub-combinations of all the ranges with all the ingredients.

[0007] The compounds A are alkanes of 8-12 carbon atoms (especially 8 or10 carbons) with at least 4 methyl and/or ethyl branches, e.g. 4-6branches, preferably 4 or 5 or especially 4 branches. Methyl branchesare preferred. The compounds usually have their longest chain of carbonatoms, hereinafter called their backbone chain, with 4-7 e.g. 4-6 chaincarbon atoms (especially 4 or 5) to which the methyl, and/or ethylbranches are attached. Advantageously, especially in relation to thefirst to tenth groupings as described further below, there are nobranched groups constituting the branches other than methyl or ethyl,and, in the backbone chain of carbon atoms, there are especially nolinear alkyl groups of more than 2 carbons nor 1,2 ethylene or 1,3propylene groups in the chain, and especially no methylene groups in thechain except as part of an ethyl group; thus there are especially non-propyl or n-butyl groups forming part of the backbone chain.Preferably there is at least one compound (A) alkane of 9-12 e.g. 9 or10 carbons, and in this case there is usually less than 50% or 10% of an8 carbon alkane compound e.g. with 3 methyl branches.

[0008] The compounds can have 1 or 2 methyl or ethyl groups attached tothe same carbon atom of the backbone chain, especially 1 or 2 methylgroups and 0 or 1 ethyl groups. The carbon atom in the backbone at whichthe branching occurs is non-terminal i.e. is an internal carbon in thebackbone chain, especially the 2, 3 and/or 4 numbered carbon in thebackbone Thus advantageously the compound has geminal methylsubstituents on position 2, 3 or 4 carbon atoms, especially position 2,but in particular position 3.

[0009] In a first grouping of compounds A, there is at least one pair ofgeminal methyl branch substituents, and they are on position 2, or thereare 2 or 3 pairs of geminal branches at least 2 pairs being on vicinal(i.e. adjacent) carbon atoms, as in a group —CMe₂—CMe₂-.

[0010] In a second grouping of the compounds A there are 1, 2 or 3 pairsof geminal methyl branch substituents on a 4-6 carbon chain backbone,and, if any Ethyl CMe₂-structure is present, then there are 2 Ethyl CMe₂groups in the compound. The compounds of the second groupingadvantageously have a MON value of at least 100.

[0011] In a third grouping of the compounds, there is one geminal methylbranch grouping i.e. —CMe₂- on the backbone, while on one or both of theadjacent carbon atoms of the backbone, there is/are one or two methyl orethyl branches/especially 1 or 2 methyl branches.

[0012] In a fourth grouping of the compounds there are one, two or threepairs of geminal methyl branches. If there are 2 or 3 pairs then atleast 2 pairs are on adjacent backbone carbon atoms, and if there isonly one pair, then they are preferably on the 2 position backbonecarbon and there is a methyl branch at least on the 3 position backbonecarbon. Such compounds usually have a RON value of at least 111.Advantageously the compounds are of 8 or 10 carbon atoms.

[0013] In a fifth grouping the compound A has 2 or 3 pairs of geminalmethyl branches at least 2 pairs being on adjacent backbone carbonatoms, and the compound has a symmetrical structure. Such compoundsusually have RON value of at least 120, and especially are of 8 or 10carbon atoms.

[0014] In a sixth grouping the compounds have a linear backbone chain of4 or 6 carbons and have 4-6 e.g. 4, 5 or 6 especially 4 methyl branches,in at least one geminal group (CMe₂) especially in the absence of a 1,2ethyl group in the backbone.

[0015] In a seventh grouping, the compounds have a linear backbone chainof 5 or 6 carbons and have 4-6 e.g. 4, 5 or 6 especially 4 branches inat least one geminal group, with the proviso that if there are 4 methylbranches and the compound contains an Ethyl CMe₂ group, then thecompound contains two such Ethyl CMe₂ groups. Such compounds are usuallyliquid at 25° C. and generally have a RON value of greater than 105.Especially there are only methyl branches; such compounds usually have aMON value of at least 101.

[0016] Advantageously in an eighth grouping the compounds A contain 1, 2or 3 carbon atoms with geminal methyl branches, and if there is only onesuch carbon atom with geminal branches, then there is/are one or twobranches on a vicinal carbon atom to the geminal one, and any ethyl —C—chain group in the backbone chain has 5 carbon atoms i.e. is (Ethyl)₂CHor Ethyl CMe₂-. Especially there are 2 or 3 vicinal carbon atoms in thebackbone, each carrying 2 methyl branches.

[0017] A particularly preferred sub-class (ninth grouping) for thecompound A is alkanes with alkyl substituents on vicinal internal carbonatoms, with a total of 4, 5 or 6 carbon atoms in said substituents.

[0018] Among this sub-class are preferred ones especially with geminalmethyl groups on internal chain carbon atoms. Particularly preferredsub-class compounds A have 4 or 5 methyl substituents on the carbonbackbone, especially with at least 2 on the same backbone carbon atom(in particular in two —CMe₂- groups) especially in a —CMe₂—CMe₂ group.

[0019] In another aspect of the invention there is provided an unleadedblend composition having a MON value of at least 81 or 85 and RON valueof at least 91 or 94, which comprises component (a) a total of at least10 or 15% of one or more branched alkane compounds A¹ of 8-12 carbons(especially with 4-7 or 4-6 backbone carbon atoms), with at least 4methyl or ethyl branches and with at least 2 backbone carbon atoms whichare secondary and/or tertiary carbon atoms, with the proviso that ifthere are only 2 such carbon atoms, then both are tertiary, there beinga minimum of at least 1, 2, 5 or 10% (by volume of the composition) ofat least one individual compound A¹, and component (b) of nature and inamount as described herein, with the preferred proviso as describedabove. In the above component A¹, which may be the same or differentfrom A, there may thus in a tenth grouping be in the backbone internal(i.e. non-terminal) carbon atoms which are (i) 2 or 3 tertiary carbons,(ii) especially vicinal ones, or (iii) 2 tertiary and one sec. carbon or(iv) 2 tertiary and one or 2 primary carbon, or (iv) 1 or 2 tertiary and1 or 2 sec subject to at least 4 branches, in particular (vi) with thetert and a sec. carbon vicinal and (vii) when there are 2 tert, theseare vicinal or non-vicinal and (viii) with 1 or 2 vicinal tert and sec.carbons subject to at least 4 branches. The compounds A¹ usually arefree from 2 primary internal backbone carbon atoms on vicinal carbonsi.e. as in 1,2-ethylene group. Preferably any primary internal backbonecarbon atoms are not between, e.g. adjacent on both sides to, a tertand/or sec, carbon on the one hand and a tert and/or sec. carbon on theother hand. Especially at least the said 2 backbone carbon atoms abovein compounds A¹ are vicinal.

[0020] In another category, the eleventh grouping is of compounds A¹which contain, with the proviso of at least 4 branched groups, (i) as atleast one end of the backbone a group of formula CHR¹R² where each of R¹and R², which are the same or different is a methyl or ethyl group or(ii) as at least one end of the backbone a group of formula CR¹R²R³where R¹ and R² are as defined above and R³ is methyl or ethyl.Preferred are such compounds A¹ which have both (i) and (ii), especiallywhen the CHR¹R² group is CHMe₂ when the compound has 8 carbons or abackbone of 5 carbons and when all internal carbon atoms in the backbonechain are secondary or tertiary.

[0021] The compounds A or A¹ may have a boiling point at 1 bar pressureof 150-175° C., 130-140° C., 110-129° C., or 90-109° C. In particularthe boiling point is preferably at least 105° C. e.g. 105-175° C., withthe preferred proviso that it is at least 112° C. such as 112-175° C.unless the compound A or A¹ has 4 alkyl branches.

[0022] In another category the compounds A or A¹ may have 4-6 methyland/or ethyl branches on a 4-7 or 4-6 carbon backbone, and especially aratio of carbon atom in branches to carbon atoms in the backbone chainof at least 0.63:1 e.g. 0.63-1.6:1 such as 0.63-1.0:1. The compoundsusually have 9 or 10 carbons, unless the above ratio is at least 0.63,0.75 or 0.9.

[0023] Preferred compounds are 3344 tetramethyl hexane (A1), 2233tetramethyl butane (A2), 2233 tetramethyl pentane (A7), 22334pentamethyl pentane (A12) 22344 pentamethyl pentane (A13) 2334tetramethyl pentane (A14) 2234 tetramethyl pentane (A15) 223344hexamethyl pentane (A16) 22446 pentamethyl heptane. Of these (A1) and(A2) are most preferred with (A7) being also very valuable.

[0024] The compounds A and A¹ are either known compounds and may be madeaccording to the published literature, or are novel and may be made byconventional methods known per se in the literature (e.g. as describedin Kirk Othmer Encyclopaedia of Chemical Technology 3rd Ed. Publ.Wiley). Examples of suitable methods of preparation are knowncarbon-carbon coupling techniques for making alkanes. The technique mayinvolve reactions of one or more usually 1 or 2 alkyl chlorides,bromides or iodides with an elemental metal of Group IA, IIA, IB or IIBof the Periodic Table in

[0025] Advanced Inorganic Chemistry by F. A. Cotton+G. Wilkinson, PubInterscience New York 2nd Ed. 1966, especially sodium, magnesium, orzinc. The alkyl halide is usually a branched chain one of 3-6 carbons,in particular with methyl or ethyl branches, and especially with thehalogen atom attached to a CMe₂ group in at least one of the alkylhalides. Preferably the halide is of formula MeCMe₂X or EtCMe₂X, where Xis Cl, B or I, and the other halide, if any, is a tertiary alkyl halideor a secondary one e.g. of formula RR¹CHX, wherein at least one of R andR¹ is a branched alkyl group e.g. of 3-5 carbons such as isopropyl ort-butyl, and the other (if any) is methyl or ethyl or a primary branchedalkyl halide e.g. of formula R¹¹CH₂X, where R¹¹ is a branched alkylgroup 4-5 carbons with methyl or ethyl branches, such as isobutyl orisoamyl. Alternatively both halides can be secondary e.g. of formulaRR¹CHX, as defined above and R¹¹¹R^(IV)CHX where R¹¹¹ is methyl or ethyland R^(IV) is as defined for R, such as isopropyl or one can besecondary (as above) and one can be primary e.g. methyl or ethyl halide.The methods of coupling optimum for any particular compound A or A¹depend on availability of the precursor alkyl halide(s) so that inaddition to the above kinds, coupling via methyl or ethyl halides withbranched alkyl halides of 6-9 carbons may also be used e.g. pentamethylethyl bromide and methyl magnesium bromide to form A2. The alkylhalide(s) can react together in the presence of the metal (as in a Wurtzreaction with sodium), or one can react first with the metal to form anorganometallic compound e.g. a Grignard reagent or organo zinc, followedby reaction of the organometallic with the other alkyl halide. Ifdesired the Grignard reagent reaction can be in the presence of a metalof Group IB or IIB, such as silver, zinc or copper (especially highactivity copper). If desired the Grignard reagent from one or both alkylhalides can be reacted with the latter metal to form other alkylmetallic species e.g. alkyl silver or alkyl copper compounds, which candisproportionate to the coupled alkane. The Grignard reagent(s) can alsoreact with a cuprous halide to form alkyl copper species fordisproportionation. Finally an organometallic compound, wherein themetal is of Group IA or IIA e.g. Li or Mg can be coupled by reactionwith a cuprous complex to give a coupled alkane. Use of only 1 alkylhalide lives a symmetrical alkane, while use of a mixture of alkylhalides gives a mixture of alkanes, usually each of the symmetricaldimers and an unsymmetrical alkane formed from both alkyl halides.

[0026] The above organometallic reactions are usually conducted underinert conditions, i.e. anhydrous and in the absence of oxygen e.g. underdry nitrogen. They are usually performed in an inert solvent e.g. a dryhydrocarbon or ether. At the end of the reaction any residualorganometallic material is decomposed by addition of a compound withactive hydrogen e.g. water or an alcohol, and the alkanes are distilledoff, either directly or after distribution between an organic andaqueous phase.

[0027] Examples of the above processes are the coupling of tertbutylchloride in the presence of Mg and diethyl ether to form compound A(2)(as described by D. T. Flood et al, J. Amer Chem. Soc. 56, (1934) 1211,or R. E. Marker et al, J. Amer Chem. Soc. 60, (1938) 2598 or F. C.Whiteman et al, J. Amer Chem. Soc. 55, (1933) 380), and thecorresponding coupling of EtCMe₂ halides to form compound A1. Otherpreparations of highly branched alkanes are described in M Tamura and J.Kochi, J. Amer. Chem. Soc. Vol.93, Part 6 (Mar. 24, 1971) and F. O.Ginah et al, J. Org. Chem. Vol. 199, 55 pp584-589 and R. Y. Levina & V.K. Daukshas, Zhur. Obschei Khiin. Vol. 29 (1959) and F L Howard et al, JRes. Nat. Bur. Standards Research Paper RP1779, Vol 38 March 1947 pp365-395. The disclosures of these documents is incorporated herein byreference.

[0028] The crude alkanes made by the above processes, especially thesymmetrical ones, may be used as such in the blends of the invention ormay be purified further e.g. by distillation first. The crudeunsymmetrical alkanes may be also purified, but are preferably used assuch as the by-product alkanes are often useful hydrocarbons for theblend, e.g. coupling of t BuX and EtCMe₂X as described above produces amixture of alkanes containing A1, A2 and A7.

[0029] Other known methods of making the alkanes A or A¹, are reactionof alkyl metallic compounds e.g. Grignard reagents with carbonylcompounds such as aldehydes, ketones, esters, or anhydrides to formbranched chain carbinols, which are dehydrated to the correspondingolefin, which is hydrogenated to the alkane. Thus 2,2,3,4-tetra methylpentane may be made from isopropyl magnesium bromide and methyl t-butylketone (followed by dehydration and hydrogenation),

[0030] Thus the present invention produces an unleaded blend compositionof MON value at least 81 or 85 and RON value at least 91 or 94 whichcomprises (a) a total of at least 10 or 15% of one or more branchedhydrocarbon compound A or A¹ there being a minimum of at least 1, 2 or5% of at least one individual compound A or A¹ and (b) at least 20% ofat least one different liquid hydrocarbon of bp60-160° C. having a MONvalue of at least 70 and RON value at least 90 especially when (b) isnot within the definition of A or A¹. Examples of the liquidhydrocarbons are paraffins, such as linear or branched chain alkanes of4-8 carbons, such as isobutane, butane, isopentane, dimethyl alkanessuch as 23 dimethyl butane, cycloalkanes, such as cyclopentane andcyclohexane, aromatics and olefins.

[0031] Another unleaded blend composition of the invention of MON valueof at least 81 or 85 and RON value of at least 91 or 94 comprisescomponent (a) as above and component (b) at least 20% of at least one ofa straight run naphtha, alkylate isomerate (bp25-80° C.) heavyreformate, light reformate (bp20-79° C.), hydrocrackate, aviationalkylate (bp30-190° C.), straight run gasoline, cracked spirit, such asheavy or light catalytic cracked spirit or steam cracked spirit. Thestraight run products are produced directly from crude oil byatmospheric distillation. The naphtha may be light naphtha of bp30-90°C. or medium naphtha of bp90-150° or heavy naphtha of bp150-220° C.

[0032] In the blends of the invention, the amount of at least oneindividual compounds A or A¹ is usually at least 1, 2 or 5%, or at least10 or 15%, such as 5-60%, e.g. 15-60%, or 8-25%, 20-35% or 30-55% or2-10%. The amount of 2,2,4-trimethyl pentane if present is usually atleast 10% of the composition. Total amounts of trimethyl pentanes in theblend are preferable less than 69% of the blend, but advantageously atleast 26% (especially when the amount of aromatics is less than 17%). Ifa 9 or 10 carbon alkane is (a), then the amount of 2,2,4-trimethylpentane is especially less than 70 or 50%. More than one such compound Aor A¹ may be present e.g. of higher and lower RON in weight ratios of9:1 to 0.5:99.5, such as 0.5:1 to 5:1 or 5:95 to 20:80, particularly formixtures of compounds A1 and A2 and/or with higher or lower boilingpoints (atmospheric pressure) e.g. those in which the compounds A and/orA¹ have boiling points differing by at least 10° C. e.g. at least 40° C.such as 10-70° C. or 20-50° C. the relative amounts being as describedabove. In the blends amounts of compounds A or A¹ of RON at least 138e.g. A1 may be 1-40%, such as 2-10 or 20-35%, while those of compounds Aor A¹ of RON 120-138 e.g. A2 may be 1-60, such as 5-60, 8-25 or 30-55%(especially when used with the higher RON compound) or 15-50% when usedas sole compound A. Total amounts of all compounds A and A¹ (if any) inthe blend are at least 10 or 15% such as 15-70 e.g. 15-60, 15-40 or30-55% or 40-60% or 10-35%.

[0033] The blend may also comprise predominantly aliphatic refinerystreams which are usually liquid e.g. at 20° C. such as naphtha,straight run gasoline (also known as light naphtha bp 25-120° C.),alkylate and isomerate. Amounts in total of these may be 10-70%, such as10-30, 30-70 or 35-65%. Amounts of naphtha may be 0-70% or 1-70% such as10-30, 30-70 or 35-65%, while amounts of light naphtha may be 0 or 1-70such as 1-20 or especially 30-65%, and amounts of medium naphtha may be0 or 1-55, such as 3-20 or 15-55%. The volume ratio of light to mediumnaphtha may be 50.1 to 1:50, such as 0.5-20:1 or 1:0.5-50. Amounts ofalkylate or isomerate (if present) may be 0.5-20% such as 1-10%, whileamounts of hydrocrackate may be 0.5-30% e.g. 10-30%. A preferred blendcomprises 20-60% compound A or A¹ and conversely 80-40% straight rungasoline, the sum of these being substantially 100%

[0034] The blends of the invention usually contain in total at least 70%of saturates, such as 70-98% or 70-90% or 90-98%.

[0035] If desired and especially for aviation gasoline, the blends maycontain a hydrocarbon component which is a saturated aliphatichydrocarbon of 4-6 carbons and which has a boiling point of less than80° C. under atmospheric pressure, such as 20-50° C., and especially isitself of Motor Octane Number greater than 88 in particular at least 90e.g. 88-93 or 90-92. Examples of the hydrocarbon component includealkanes of 4 or 5 carbons in particular iso-pentane, which may besubstantially pure or crude hydrocarbon fraction from reformate orisomerate containing at least 30% e.g. 30-80% such as 50-70%, the maincontaminant being up to 40% mono methyl pentanes and up to 50% dimethylbutanes. The hydrocarbon component may be an alkane of boiling point (atatmospheric pressure) −20° C. to +20° C. e.g. n and/or iso butaneoptionally in blends with the C₅ alkane of 99.5:0.5 to 0.5:99.5, e.g.88:12 to 75:25. n Butane alone or mixed with isopentane is preferred,especially in the above proportions, and in particular with a volumeamount of butane in the composition of up to 20% such as 1-15% e.g. 1-8,3-8 or 8-15%, especially 1-3.5%.

[0036] The hydrocarbon component boiling less than 80° C., in particularisopentane, may also be present in compositions of the invention whichcontain at least one compound A or A¹, of at least 10 carbon atoms, inparticular those boiling at 160° C. or above, such as A1, and A12-14.Relative amounts of these compounds A or A¹ to the low boiling componente.g. isopentane, may be 1-9:9-1 such as 5-9.5-1, especially with lessthan 20% of A or A¹ in the composition.

[0037] Cycloaliphatic hydrocarbons e.g. of 5-7 carbons such ascyclopentane or cyclohexane may be present but usually in amounts ofless than 15% of the total e.g. 1-10%.

[0038] The compositions of the invention also preferably contain ascomponent (d) at least one olefin, (in particular with one double bondper molecule) which is a liquid alkene of 5-10 e.g. 6-8 carbons, such asa linear or branched alkene e.g. pentene, isopentene hexene, isohexeneor heptene or 2 methyl 2 pentene, or a mixture comprising alkenes whichmay be made by cracking e.g. catalytically or thermally cracking aresidue from crude oil, e.g. atmospheric or vacuum residue; the mixturemay be heavy or light catalytically cracked spirit (or a mixturethereof). The cracking may be steam assisted. Other examples of olefincontaining mixtures are “C6 bisomer”, catalytic polymerate, and dimate.The olefinic mixtures usually contain at least 10% w/w olefins, such asat least 40% such as 40-80% w/w. Preferred mixtures are (xi) steamcracked spirit (xii) catalytically cracked spirit (xiii) C6 bisomer and(xiv) catalytic polymerate, though the optionally cracked catalyticallyspirits are most advantageous. Amounts in the total composition of theolefinic mixtures especially the sum of (xi)-(xiv) (if any present)maybe 0-55, e.g. 10-55 or 18-37 such as 23-35 or 20-55 such as 40-55% A(xi) and (xii) (if present) in total in the composition are preferably18-55, such as 18-35, 18-30 or 35-55% (by volume).

[0039] The olefin or mixture of olefins usually has an MON value of70-90, usually a RON value of 85-95 and a ROAD value of 80-92.

[0040] The volume amount of olefin(s) in total in the gasolinecomposition of the invention may be 0% or 0-30%, e.g. 0.1-30% such as1-30% in particular 2-25 e.g. 2-14% (especially 3-10). Usually thecomposition contains at least 1% olefin and a maximum of 18% orespecially a maximum of 14%, but may be substantially free of olefin.

[0041] The compositions may also contain as component (e) at least onearomatic compound, preferably an alkyl aromatic compound such as tolueneor o, m, or p xylene or a mixture thereof or a trimethyl benzene Thearomatics may have been added as single compounds e.g. toluene, or maybe added as an aromatics mixture containing at least 30% w/w aromaticcompounds such as 30-100% especially 50-90%. Such mixtures may be madefrom catalytically reformed or cracked gasoline obtained from heavynaphtha Example of such mixtures are (xxi) catalytic reformate and(xxii) heavy reformate or heavy steam cracked spirit. Amounts of thesingle compounds e.g. toluene in the composition may be 0-35%, such as2-33% e.g. 10-33%, while amounts of the aromatics mixtures especiallythe total of the reformates (xxi) & (xxii) (if any) in the compositionmay be 0-50%, such as 1-33% e.g. 2-15% or 2-10% or 15-32% v/v, and totalamount of reformates (xxi), (xxii) and added single compounds (e.g.toluene) may be 0-50% e.g. 0.5-20% or 5-40, such as 15-35 or 5-25% v/v.

[0042] The aromatics usually have a MON value of 90-110 e.g. 100-110 anda RON value of 100-120 such as 110-120 and a ROAD value of 95-110. Thevolume amount of aromatic compounds in the composition is usually 0% or0-50% such as less than 40% or less than 28% or less than 20% such as1-50%, 2-40%, 3-28%, 4-25%, 5-20% (especially 10-20%), 4-10% or 20-35%especially of toluene. The gasoline composition may also besubstantially free of aromatic compound. Amounts of aromatic compoundsof less than 42%, e.g. less than 35% or especially less than 30% or 18%are preferred.

[0043] Preferably the amount of benzene is less than 5% preferably lessthan 1.5% or 1% e.g. 0.1-1% of the total volume or less than 0.1% of thetotal weight of the composition.

[0044] The compositions may also contain as component (f) at least oneoxygenate octane booster, usually of Motor Octane Number of at least96-105 e.g. 98-103. The oxygenate may be any organic liquid moleculecontaining and preferably consisting of, CH and at least one oxygen atome.g. 1-5 of bp less than 225° C. The octane booster is usually an ethere.g. a dialkyl ether, in particular an asymmetric one, preferablywherein each alkyl has 1-6 carbons, in particular one alkyl being abranched chain alkyl of 3-6 carbons in particular a tertiary alkylespecially of 4-6 carbons such as tert-butyl or tert-amyl, and with theother alkyl being of 1-6 e.g. 1-3 carbons, especially linear, such asmethyl or ethyl. Examples of such oxygenates include methyl tertiarybutyl ether (MTBE), ethyl tertiary butyl ether and methyl tertiary amylether. The oxygenate may also be a cyclic ether, in particular with 5 or6 ring atoms in the or each ring, such as furan or tetrahydrofuran andits lower alkyl e.g. methyl derivatives. The oxygenate may also be analcohol of 1-6 carbons e.g. ethanol. The oxygenate may also be anorganic carbonate e.g. a dialkyl carbonate with 1-3 carbon atoms in eachalkyl e.g. dimethyl carbonate.

[0045] The volume amount of the oxygenate may be 0 or 0-25% such as1-25%, 2-20%, 2-10% or 5-20% especially 5-15%, but advantageously lessthan 3% such as 1-3% (especially of MTBE and/or ethanol). The oxygenatemay also be substantially absent from the composition or gasoline of theinvention, which is thus a substantially hydrocarbon fuel.

[0046] The present invention also provides a formulated unleadedgasoline comprising a blend composition of the invention comprisingcomponent (a) and (b) and usually at least one gasoline additive, e.g.as described above, in particular with the gasoline comprising less than5%, e.g. less than 4% of triptane or 223 trimethyl pentane.

[0047] The blend of the invention contains at least one component (a)and component (b) and, (optionally (c) to (f), as well, and theformulated unleaded gasoline also contains at least one gasolineadditive e.g. a motor gasoline or aviation gasoline additive, forexample as listed in ASTM D-4814 the contents of which is hereinincorporated by reference or specified by a regulatory body, e.g. USCalifornia Air Resources Board (CARB) or Environmental Protection Agency(EPA). These additives are distinct from the liquid fuel ingredients,such as MTBE. Such additives may be the lead free ones described inGasoline and Diesel Fuel Additives, K Owen, Publ. By J. Wiley,Chichester, UK, 1989, Chapters 1 and 2, U.S. Pat. No. 3,955,938, EP0233250 or EP 288296, the contents of which are herein incorporated byreference. The additives maybe pre-combustion or combustion additives.Examples of additives are anti-oxidants, such as one of the amino orphenolic type, corrosion inhibitors, anti-icing additives e.g. glycolethers or alcohols, engine detergent additives such as ones of thesuccinic acid imide, polyalkylene amine or polyether amine type andanti-static additives such as ampholytic surface active agents, metaldeactivators, such as one of thioamide type, surface ignition inhibitorssuch as organic phosphorus compounds, combustion improvers such asalkali metal salts and alkaline earth metal salts of organic acids orsulphuric acid monoesters of higher alcohols, anti valve seat recessionadditives such as alkali metal compounds, e.g. sodium or potassium saltssuch as borates or carboxylates e.g. sulpho succinates, and colouringagents, such as azodyes. One or more additives (e.g. 2-4) of the same ordifferent types may be used, especially combinations of at least oneantioxidant and at least one detergent additive. Antioxidants such asone or more hindered phenols e.g. ones with a tertiary butyl group inone or both ortho positions to the phenolic hydroxyl group are preferredin particular as described in Ex. 1 hereafter. In particular theadditives may be present in the composition in amounts of 0 1-1000 ppme.g. 1-20 ppm of each, usually of an antioxidant especially one or morehindered phenols. Total amounts of additive are usually not more than1000 ppm e.g. 1-1000 ppm.

[0048] The compositions and gasolines are free of organolead compounds,and usually of manganese additives such as manganese carbonyls.

[0049] The compositions and gasolines may contain up to 0.1% sulphur,e.g. 0 000-0.02% such as 0.002-0.01% w/w.

[0050] The gasoline compositions of the invention usually have a MONvalue of 80 to 105 such as 85-105, 85-90, 90-105 or 93-105 e.g. butespecially 94-102. The RON value is usually 90-115 e.g. 102-115 such as98-112 or 105-112, or 93-98 e.g. 94.5-97.5, or 97-101 while the ROADvalue is usually 85-110 or 85-107 e.g. 98-106 or 102-108 or 85-95.Preferred gasoline compositions have MON 83-93, RON 93-98 and ROAD 85-95or MON 85-90, RON 94-101 and ROAD 89-96 but especially MON 93-98, RON102-108, ROAD 98-106, or MON 95-105, RON 102-115 e.g. 108-115 and ROAD98-106. The Net calorific value of the gasoline (also called theSpecific Energy) is usually at least 18000 BtuAb e.g. at least 18500,18700 or 18,900 such as 18500-19500, such as 18700-19300 or 18900-19200;the calorific value may be at least 42MJ/kg e.g. at least 43.5 MJ/kgsuch as 4245 or 43-45 such as 43.5-44.5MJ/Ikg. The gasoline usually hasa boiling range (ASTM D86) of 20-225° C., in particular with at most 5%e.g. 0-5% or 1-3% boiling in the range 161-200° C. The gasoline isusually such that at 70° C. at least 10% is evaporated while 50% isevaporated on reaching a temperature in the range 77-120° C. preferably77-116° C. and by 185° C., a minimum of 90% is evaporated. The gasolineis also usually such that 8-50% e.g. 10-40% may be evaporated at 70° C.,40-74% at 100° C., 70-99.5% at 150° C. and 90-100% may be evaporated at180° C.; preferably 46-65% has been evaporated by 100° C. The ReidVapour Pressure of the gasoline at 37.8° C. measured according to ASTMD323 is usually 30-120, e.g. 40-100 such as 61-80 or preferably 50-80,40-65, e.g. 45-65, 40-60 or 40-50 Kpa. Especially the gasoline or blendhas RON value of 90-115, MON value of 85-105, aromatics content of lessthan 35%, olefins content of less than 14%, benzene less than 1%, %evaporated at 70° C. 10-40%, % evaporated at 100° C. 40-74%, %evaporated at 150° C. 70-99.5% and RVP of 40-60 kPa.

[0051] The gasoline compositions, when free of any oxygenates usuallyhave a H:C atom ratio of at least 1.8.1 e.g. at least 2.0:1 or at least2.1 or 2.2:1, such as 18-2.3:1 or 2.0-2.2:1. Advantageously the gasolinecomposition meets the following criteria.${{{Atom}\quad H\text{:}C \times \left\lbrack {1 + {oxy}} \right\rbrack \times \left\lbrack {{{Net}\quad \frac{{Heat}\quad {of}}{200}\quad {Combustion}} + {ROAD}} \right\rbrack} \geq y},$

[0052] wherein Atom H:C is the fraction of hydrogen to carbon in thehydrocarbons in the composition, oxy means the molar fraction ofoxygenate, if any in the composition, Net Heat of Combustion is theenergy derived from burning 1lb (454 g) weight of fuel (in gaseous form)in oxygen to give gaseous water and carbon dioxide expressed in Btu/lbunits [MJ/kg times 430.35], and y is at least 350, 380, 410 or 430, inparticular 350-440 e.g. 380-420 especially 400-420.

[0053] Among preferred blends of the invention are unleaded blendscomprising as component (a) at least 5 or 10% of at least one individualcompound A or A¹ and component (b) as defined above, with the provisothat when the compound A or A¹ is an alkane of 9 or 10 carbon atoms,then blend contains at least 10% of an alkane of 6 or 7 carbons of MONat least 70 and RON at least 90, and preferably contains less than 5% intotal of 2,2,3-trimethyl pentane and 2,2,3-trimethyl butane.

[0054] Preferred formulated unleaded gasolines of the invention compriseat least one gasoline additive and the preferred unleaded blend above,with the proviso when the compound A or A¹ is an alkane of 9 or 10carbon atoms, the blend preferably contains less than 5% in total of2,2,3-trimethyl pentane and 2,2,3-trimethyl butane.

[0055] Preferred blends and gasolines of the invention can have MONvalues of 94-105 (e.g. 97-105), RON values of 103-115 (e.g. 107-115),ROAD values of 98-110 (e.g. 102-110), compound A or A¹ contents of30-60% e.g. 40-60% (comprising 1 or 2 compounds A or A¹ especially A1and/or A2), total naphtha contents of 35-65% (e.g. 35-55%) and 1-5%butane, the blends containing 1-8% e.g. 2-6% aromatics, 0-1% olefins and91-99% (e.g. 94-98%) saturates. These are substantially aliphatic blendsand gasolines of very high octane numbers, without the use of oxygenatessuch as MTBE, and also substantially saturated.

[0056] Other very high octane blends and gasolines of the invention canhave MON values of 94-102 e.g. 94-99, RON values of 105-115, ROAD valuesof 99-107, compound A or A¹ contents of 30-60% e.g. 30-50% (comprising 1or 2 compounds A or A¹ especially A1 and/or A2), medium naphtha contentsof 5-30% and contents of total olefinic fraction such as steam crackedspirit of30-50% and 1-5% butane, the blends containing 10-25% aromaticse.g. 12-18% aromatics, 4-14% olefins e.g. 6-12%, and 60-90% such as70-80% saturates. These high octane materials are obtained without theuse of oxygenates.

[0057] Further blends and gasolines of the invention can have MON valuesof 84-90, RON values of 93-98, ROAD values of 86-94, and containcompound A or A¹ in amount of 15-35% (especially of A2), total naphthaof 40-65% and olefinic fractions such as steam cracked spirit of 15-45%and 0 or 1-5% butane, with aromatic contents of 5-25% such as 10-18%olefin contents of 2-14% and saturate contents of 70-90%.

[0058] Other blends and gasolines of the invention can contain 10-35%compound A or A¹ (especially A2), and naphtha 30-50%, hydrocrackate10-30% alkylate and/or isomerate 2-10%, and reformate 3-12%.

[0059] Other blends and gasolines of the invention can contain 10-35%compound A or A¹ (especially A2) and 3-12% reformate, 1-20% lightnaphtha/straight run gasoline, as well as alkylate and isomerate, theblend and gasoline preferably containing at least 70% of saturates.

[0060] The invention can provide motor gasolines, in particular of 91,95, 97, 98 and 110 RON values, with desired high Octane Levels but lowemission values on combustion in particular of at least one of totalhydrocarbons, NOx, carbon monoxide, and carbon dioxide, especially ofboth total hydrocarbons and carbon dioxide. Thus the invention alsoprovides the use of a compound A particularly A1 or A2 in unleadedgasoline of MON at least 80 e.g. 80 to less than 98, e.g. as an additiveto or component therein, to reduce the emission levels on combustion,especially of at least one of total hydrocarbons, NOx, carbon monoxideand carbon dioxide especially both of total hydrocarbons and carbondioxide. The invention also provides a method of reducing emissions ofexhaust gases in the combustion of unleaded gasoline fuels of MON of atleast 80 which comprises having at least 10% component (a), inparticular Al or A2, present in the fuel which is a gasoline of theinvention. The invention also provides use of an unleaded gasoline ofthe invention in a spark ignition combustion engine to reduce emissionsof exhaust gases. In the compositions, gasolines, methods and uses ofthe invention the component (a) is preferably used in anemission-reducing effective amount. The compositions of the inventionmay be used in supercharged or turbocharged engines, or in normallyaspirated ones. The compound A, preferably A1 or A2, can reduce one ormore of the above emission levels better than a mixture of aromatics andoxygenate at similar Octane Number and usually decrease the fuelconsumption as well.

[0061] The gasolines of the invention may be used in internal combustionspark ignition engines. They may be used to power moving vehicles onland and/or sea and/or in the air; the invention also provides a methodof moving such vehicles by combustion of a gasoline of the invention.The vehicle usually has a driver and especially means to carry at leastone passenger and/or freight.

[0062] The engine sizes for motor gasoline use are usually at least 45cc e.g. 45-10000 cc e.g. at least 200 cc, such as 500-10000 cc, inparticular 950-2550, such as 950-550, or 1250-1850 cc, or 2500 -10000 ccsuch as 2500-5000 or 5000-9000 cc. The engines have at least 1 cylinder,but preferably at least 2 or 3 cylinders, e.g. 3-16, especially 4-6 or 8cylinders; each cylinder is usually of 45-1250 cc e.g. 200-1200 cc, inparticular 240-520 cc or 500-1000 cc. The engines may be 2 strokeengines, but are preferably 4 stroke.

[0063] Rotary engines e.g. of the Wankel type may be used. The motorengines may be used to power vehicles with at least 2 wheels e.g. 2-4powered wheels, such as motor bicycles, tricycles, and 3 wheeled cars,vans and motor cars, in particular those vehicles legislated for use ona public highway but also off road e.g. 4 wheeled drive vehicles, sportscars for highway use, and racing cars, including drag racing cars andtrack racing cars. Power from the engine will preferably be connected tothe driving wheels via a gearbox and clutch system, or other form ofdrive train system, to achieve the transition from a stationary to amobile state. The engine and drive train will best allow a range ofactual vehicle road speed of between 1-350 km/h, preferably between5-130 km/h and allow for continuous variation of speed thereof The roadspeed of the vehicle is usually reduced by a braking mechanism fitted tothe vehicle, the braking being generally applied by friction. The enginemay either by air or water cooled, the air motion induced by a movingvehicle being used to directly, or indirectly cool the engine. Thevehicle comprises a means to facilitate a change of vehicle direction,e.g. a steering wheel or stick. Usually at least 10% of the vehicledistance travelled is carried out at greater than 5 km/h.

[0064] The engines using aviation gasoline are usually in piston drivenaircraft, i.e. with at least one engine driving a means for mechanicallymoving air such as at least one propeller. Each engine usually drives atleast one propeller driving shaft with 1 or 2 propellers. The aircraftmay have 1-10 propellers e.g. 2-4. The aircraft engines usually have atleast 2 cylinders, e.g. 2 to 28 cylinders, each of which is preferablygreater than 700 cc in volume, such as 700-2000 cc e.g. 1310 cc. Thetotal engine size is usually 3700-50000 cc e.g. 3700 to 12000 cc forsingle or twin engined passenger light aircraft, 12000 to 45000 cc for 2or 4 engined freight or airline use (e.g. 15-200 passengers, such as 50to 150 passengers). The engines may have an engine power to weight ratioof at least 0.3 Hp/lb wt of engine, e.g. 0.3-2 Hp/lb, and may have apower to cylinder volume of at least 0.5 (Hp/cu.in) e.g. 0.5-2.Cylinders may be arranged in rows, V formation, H formation, flat(‘horizontally opposed’) or radially around a common propeller driveshaft. One or more rows/circles of cylinders may be used, e.g. flat 2,flat 4, flat 6, V12, 1 2or 3 circles of 7 cylinders etc. Every cylinderhas one and more preferably at least two spark plugs. A gear system mayoptionally be used to drive the propeller and or a superchargerAlternatively, an exhaust turbo charger may also be present. Exhaustoutlets may be individual or run into a common manifold and preferablypoint in the opposite direction to forward flight. Fins may be presenton the exterior of the engine for air cooling. Greater than 90% of thedistance travelled by the engine, when in use, is usually spent at 500feet or more above ground level. Typically, during greater than 90% ofthe time when the engine is running, the engine operates at above 1000rpm e.g. between 1000 to 3500 rpm.

[0065] The aircraft usually has at least one tank having a capacity ofat least 1001, especially with a total capacity of at least 10001. Smalland micro-light aircraft may have tanks substantially smaller incapacity but can operate on the unleaded gasoline described.

[0066] The gasolines of the invention may be made in a refinery byblending the ingredients to produce at least 200,0001/day of gasolinesuch as 1-10 million 1/day. The gasoline may be distributed to aplurality of retail outlets for motor gasoline, optionally via wholesaleor bulk outlets e.g. holding tanks, such as ones of at least 2 million 1capacity e.g. 5-15 million 1. The distribution may be by pipeline or intanks transported by road, rail or water, the tanks being of at least50001 capacity. At the retail sites e.g. filling station, the motorgasoline is dispensed to a plurality of users, i.e. the drivers of thevehicles, e.g. at a rate of at least 100 or 1000 different users perday. For aviation use, the gasoline is usually made in a refinery toproduce at least 1000 barrels per day (or 100,0001/day) such as 0.1-2million 1/day. The avgas is usually distributed by tanker by road, railor water, or pipelines directly to the airport distribution or holdingtanks, e.g. of at least 300,0001 capacity, from whence it is distributedby pipeline or tanker (e.g. a mobile refuelling bowser to fuel aplurality of aircraft, e.g. at least 5/day per tank; the aircraft mayhave one or more on-board tank each of at least 1001 capacity.

[0067] The present invention is illustrated in the following Examples.

EXAMPLES 1-7

[0068] Various unleaded blends are made up with compound A1 and/or A2and various refinery streams as shown in Table 1.

[0069] 7 Formulated gasolines are made, each containing one of the aboveblends and a 15 mg/l of a phenolic antioxidant 55% minimum 2,4dimethyl-6-tertiary butyl phenol 15% minimum 4methyl-2,6-ditertiary-butyl phenol with the remainder as a mixture ofmonomethyl and dimethyl-tertiary butyl phenols.

[0070] In each case the gasolines are tested for MON and RON, and theirReid Vapour Pressure at 37.8° C. The results are shown in table 1, whichalso shows their analyses and distillation profile (according to ASTMD86).

EXAMPLE 8

[0071] The emission characteristics on combustion of the formulatedgasolines of Ex. 1-7 are determined.

[0072] The fuels are tested in a single cylinder research engine at aspeed/load of 50/14.3 rps/Nm with a LAMBDA setting of 1.01, and theignition setting is optimised for the comparative blend. The emissionsof CO, CO₂ total hydrocarbons, Nox, are measured from the exhaust gases.The results are averaged and show a reduction in the emissions comparedto a standard unleaded fuel.

EXAMPLE 9 And Comparative Ex. A

[0073] An unleaded blend was made up with 22446 pentamethyl heptane,blended with various refinery streams as shown in Table 3. Comp Ex. A,with heavy reformate meets the Europe 2005 requirement for high octanefuel with RON 97.0, MON 86.3 RVP at 37.8° C 54.7 kPa distillationprofile according to ASTM D86, 10% evap, at 52.9° C. 50% at 107.0° C.and 90% at 166.1° C.

[0074] 2 formulated gasolines were made, each containing one of theabove blends and 15 mg/l of the phenolic antioxidant used in Ex. 1-7

[0075] In each case the gasolines were analysed. The results are shownin table 3.

[0076] The emission characteristics on combustion of the formulatedgasolines of Ex. 9 and Comp. A were determined.

[0077] The fuels were tested as in Ex. 1-7 in a single cylinder researchengine at a speed/load of 20/7/2 rps/Nm with LAMBDA setting of 1.01, andthe ignition setting was optimised for the comparative blend A. Theemissions of CO, CO₂ total carbon oxides, total hydrocarbons, NO_(x)were measured from the exhaust gases as was the Fuel Consumption(expressed in g/h¹Whr). The results were averaged and compared to thecomparative Ex.A. The degrees of change were as given in Table 4. TABLE3 Comp A Formulation % v/v Base Fuel 8 Butane 3 3 Full rangecatalytically 20 20 cracked spirit Alkylate 40 40 Light hydrocracked 7 7spirit Full range steam 10 10 cracked spirit Heavy reformate 202,2,4,4,6-Pentamethylheptane 20 Density kg/l 0.7487 0.7264 C:H 1:1.8891:2.076 C % w/w 86.4 85.25 H % w/w 13.6 14.75 Benzene % v/v 0.6 0.6Aromatics % v/v 29.4 9.4 Olefins % v/v 9.0 9.0

[0078] TABLE 4 Fuel Example CO CO2 COx THC NOx Economy Comp A     0%  0.0%   0.0% 0.0%   0.0% 0.0% 9 −1.7% −2.7% −2.7% 3.1% −4.5% 0.1%

[0079] TABLE 1 Ex. 1 2 3 4 5 6 7 Butane 47 36 54 28 2.9 cpd A2 20.0 10.049.2 28.0 41.6 24.1 20.4 cpd A1 27.2 26.4 4.7 — — Med Naphtha 7.4 0.0727.3 48.0 17.9 23.7 Light Naphtha 43.2 60.6 13.6 1.5 — 41.1 35.4Hydrocrackate 21.5 Reformate 7.8 Alkylate 5.6 Steam Crack Spirit 19.737.6 20.4 % Aromatics 4.0 4.7 3.6 11.6 15.2 12.3 % Olefins 0.2 0.2 0.15.2 9.7 5.5 % Saturates 95.8 95.1 96.3 83.2 75.1 82.2 RON 110.0 104.5110.0 95.0 110.0 95.0 MON 100.0 95.5 100.0 86.0 96.9 86.0 RVP .kPa 50.060.0 50.0 50.0 50.0 52.3 ROAD 105 100 105 90.5 103.45 90.5 E70% v/v 22.833.4 10.5 16.7 19.0 31.4 E100% v/v 49.9 60.0 49.0 49.0 51.1 53.5 E150%v/v 78.0 78.0 99.0 96.9 99.0 78.0 E180% v/v 92.8 92.6 100.0 99.8 100.093.2 Benzene % v/v 0.3 0.03 0.3 0.12 0.23 0.12 Sulphur % w/v 0.00050.0005 0.0004

EXAMPLE 10

[0080] An unleaded blend was made up with 2,2,3,3-tetramethyl butane(12%), alkylate (45%), reformate (6%), isomerate (20%) and naphtha i.e.a straight sum gasoline (17%). The tetramethyl butane contained 86.6%,2,2,3,3-tetramethyl butane, 3.6% 2,2,4-trimethyl pentane 3.7%, cis 3methyl hexene 2 and 6% unknown and high boilers. It was madesubstantially according to the procedure of Marker and Oakwood J. Amer.Chem. Soc. 1938, 60, 258.

[0081] The blend was mixed with 15 mg/l of the phenolic antioxidant usedin Ex. 1-3. The formulated gasoline was tested for MON and RON whichwere found to be 88.7 and 93.0 respectively, ROAD value 90.85.

1. Use of component (a), which is at least one branched chain alkane of8-12 carbon atoms with at least 4 branches, which are methyl or ethyl,in an unleaded gasoline of MON at least 80 to reduce the emission levelson combustion of said gasoline.
 2. A method of reducing emissions ofexhaust gases in the combustion of an unleaded gasoline fuel of MON atleast 80 which comprises having present in said gasoline at least 5 or10% of component (a) as defined in claim
 1. 3. Use in a spark ignitioncombustion engine of an unleaded gasoline fuel of MON at least 80 whichcomprises at least 5 or 10% of component (a) as defined in claim 1 toreduce emissions of exhaust gases.
 4. Use or method according to any oneof claims 1-3 wherein the gasoline is an unleaded motor gasoline.
 5. Useor method according to any one of claims 1-3 wherein the gasoline is anunleaded aviation gasoline.
 6. Use or method according to any one of thepreceding claims wherein said gasoline comprises at least 10 or 15% intotal by volume of said branched chain hydrocarbon.
 7. Use or methodaccording to claim 6 wherein said gasoline comprises at least 10 or 15%by volume of at least one branched chain hydrocarbon, which has 8-12carbons and 4 methyl branches, and there being a minimum of at least1,2, 5 or 10% by volume of at least one of such individual branchedchain hydrocarbons.
 8. Use or method according to claims 6 or 7 whereinthe gasoline comprises 15-60% of said component (a).
 9. Use or methodaccording to any one of the preceding claims wherein in the saidbranched chain hydrocarbon, there are 1, 2 or 3 pairs of geminal methylbranch substituents on a 4-6 carbon chain backbone, and if any ethylCMe₂ structure is present, then there are 2 ethyl CMe₂ groups in themolecule, and no n-propyl group forms part of the backbone chain
 10. Useor method according to claim 9 wherein said branched chain hydrocarbonhas 2 or 3 pairs of geminal methyl branches.
 11. Use or method accordingto claim 10 wherein said hydrocarbon is at least one of2,2,3,3-tetramethyl butane and 3,3,4,4-tetramethyl hexane.
 12. Use ormethod according to any one of the preceding claims wherein saidgasoline comprises a blend composition with a MON value of at least 81and RON value of at least 91 and also comprises at least one component(b), which is at least one liquid hydrocarbon or mixture thereof ofbp60-160° C. having a MON value of at least 70 and RON value of at least90, the total amount of component (b) being at least 20%.
 13. Use ormethod according to any one of claims 1-11 wherein said gasolinecomprises a composition of MON value at least 81 and RON value of atleast 91 which also comprises at least one component (b) which is atleast 20% in total of one or more refinery streams, such that said blendcomposition contains in total at least 70% of saturated hydrocarbons.14. Use or method as claimed in any one of the preceding claims whereinthe gasoline or blend composition has RON value of 90-115, MON value of85-105, aromatics content of less than 35%, olefins content of less than14%, benzene less than 1%, % evaporated at 70° C. 10-40%, % evaporatedat 100° C. 40-74%, % evaporated at 150° C. 70-99.5 and RVP of 40-60 kPa15. A formulated unleaded gasoline which comprises at least one motor oraviation gasoline additive, and at least one of an unleaded gasoline ofMON at least 80 and a blend composition, each as defined in any one ofclaims 1-14.
 16. An unleaded gasoline according to claim 15 in whichwhen the branched chain hydrocarbon is an alkane of 9 or 10 carbonatoms, then the blend composition contains less than 5% in total of2,2,3-trimethyl pentane and 2,2,3-trimethyl butane.
 17. A gasolineaccording to claim 15 or 16 which is a motor gasoline.
 18. An unleadedblend composition having a Motor Octane Number (MON) of at least 81 andResearch Octane Number (RON) of at least 91 which comprises component(a) a total of at least 10% preferably at least 15% by volume of theblend composition of at least one branched chain hydrocarbon, which isan alkane of 8-12 carbon atoms with at least 4 methyl or ethyl branches(hereinafter called a compound (A)) there being a minimum of at least 1,5 or 10% by volume (of the blend composition), of at least oneindividual compound (A), and component (b) at least one liquidhydrocarbon or mixture thereof of bp60-160° C. having a MON value of atleast 70 and RON value of at least 90, the total amount of component (b)being at least 20%.
 19. A blend composition according to claim 18wherein when the said branched chain hydrocarbon is an alkane of 9 or 10carbon atoms, the blend contains at least 10% of an alkane of 6 or 7carbons of MON at least 70 and RON at least
 90. 20. An unleaded blendcomposition of MON value of at least 81 and RON value of at least 91which comprises at least 10% component (a) as defined in claim 18 or 19and as component (b) at least 20% in total of one or more refinerystreams, such that the blend composition contains in total at least 70%of saturated hydrocarbons.
 21. An unleaded blend composition accordingto any one of claims 18-20, wherein said hydrocarbon is as defined inany one of claims 9-11 or said composition is as defined in claim 14.